Tanning agents and preservatives

ABSTRACT

Aqueous formulations are prepared by a process wherein at least one cyclic compound of the formula I  
                 
 
is heated in the presence of water and of an acidic catalyst and, during or after the heating, H—X—R 3  is at least partially separated off, where, in formula I, 
     X is selected from oxygen, sulfur and N—R 6 ,    R 3  and R 6  are identical or different and are selected from C 1 -C 12 -alkyl, C 3 -C 12 -cycloalkyl, substituted or unsubstituted, C 7 -C 13 -aralkyl, C 6 -C 14 -aryl, substituted or unsubstituted, formyl, CO—C 1 -C 12 -alkyl, CO—C 3 -C 12 -cycloalkyl, substituted or unsubstituted, CO—C 7 -C 13 -aralkyl, CO—C 6 -C 14 -aryl, where, if X is N—R 6 , R 3  and R 6  may be linked to one another with formation of a ring;    R 1 , R 2  and R 4  are identical or different and are selected from hydrogen, C 1 -C 12 -alkyl, C 3 -C 12 -cycloalkyl, substituted or unsubstituted, C 7 -C 13 -aralkyl, C 6 -C 14 -aryl, substituted or unsubstituted, it being possible in each case for two neighboring radicals to be linked to one another with formation of a ring; n is an integer from 1 to 4;    R 5  are identical or different and are selected from hydrogen, C 1 -C 12 -alkyl, C 3 -C 12 -cycloalkyl, substituted or unsubstituted, C 7 -C 13 -aralkyl, C 6 -C 14 -aryl, substituted or unsubstituted, it being possible for R 5  to be linked to R 4  or in each case two neighboring radicals R 5  to be linked to one another with formation of a ring.

The present invention relates to a process for the preparation ofaqueous formulations, wherein at least one cyclic compound of theformula I

is heated in the presence of water and of an acidic catalyst and, duringor after the heating, H—X—R³ is separated off at least partially, where,in formula I,

-   X is selected from oxygen, sulfur and N—R⁶,-   R³ and R⁶ are identical or different and are selected from    C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted,    C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or unsubstituted, formyl,    CO—C₁-C₁₂-alkyl, CO—C₃-C₁₂-cycloalkyl, substituted or unsubstituted,    CO—C₇C₁₃-aralkyl, CO—C₆-C₁₄-aryl, where, if X is N—R⁶, R³ and R⁶ may    be linked to one another with formation of a ring;-   R¹, R² and R⁴ are identical or different and are selected from    hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or    unsubstituted, C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or    unsubstituted, it being possible in each case for two neighboring    radicals to be linked to one another with formation of a ring;-   n is an integer from 1 to 4;-   R⁵ are identical or different and are selected from hydrogen,    C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted,    C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or unsubstituted, it being    possible for R⁵ to be linked to R⁴ or in each case two neighboring    radicals R⁵ to be linked to one another with formation of a ring.

The present invention furthermore relates to aqueous formulationsprepared by the novel process, and the use of the novel aqueousformulations for the production of semifinished products or leather andof pulverulent formulations, which in turn can be used for theproduction of leather and as preservatives. Finally, the presentinvention relates to leather and semifinished products producedaccording to the invention.

Chrome tanning has been an important chemical treatment in leatherproduction for more than 100 years, cf. for example Ullmann'sEncyclopedia of Industrial Chemistry, Volume A15, pages 259 to 282 andin particular page 268 et seq., 5th Edition (1990), Verlag ChemieWeinheim. For ecological reasons, however, alternatives to chrometanning are being sought.

Processes in which some or all of the chromium has been replaced byorganic tanning agents are furthermore known. An example is the use ofthe so-called syntans, i.e. sulfonated condensates of formaldehyde andphenol or sulfonated naphthalene/formaldehyde condensates. A furtherexample is the use of so-called vegetable tanning agents. However, bothclasses of tanning agents result in a high COD of the wastewaters andlikewise give rise to reservations for environmental reasons. Moreover,it has been found that the lightfastness of the leathers is oftenunsatisfactory when sulfonated phenol/formaldehyde condensates are used(Ullmann's Encyclopedia of Industrial Chemistry, Volume A15, pages 259to 282 and in particular page 270 et seq., 5th Edition (1990), VerlagChemie Weinheim).

Furthermore, tanning with the use of aldehydes, in particulardialdehydes, for example glutardialdehyde, is known, cf., for example,H. Herfeld, Bibliothek des Leders, Volume III, page 191, Umschau VerlagFrankfurt/Main, 1984. A disadvantage is, however, that, with smallamounts of glutardialdehyde, for example from 0.5 to 0.9% by weight,based on the pelt weight, the shrinkage temperatures are not above 70°C. and at that the semifinished products produced can therefore bedewatered only to an insufficient extent. During the shaving, glueformation occurs on the flesh side of the leather and adversely affectsthe quality of the leather.

In the literature, glutardialdehyde is often also referred to asglutaraldehyde, and both expressions are used in an equivalent waybelow.

When relatively large amounts of glutardialdehyde are used, work safetyproblems may arise owing to the toxic properties of theglutardialdehyde. Moreover, it is observed that completely tannedleather is generally obtained and that the subsequent variableprocessing, as desired in many tanneries, is no longer possible.

It is known that glutardialdehyde can be used in partly or completelyacetalated form for tanning, for example as methylacetal (Ullmann'sEncyclopedia of Industrial Chemistry, Volume A15, pages 259 to 282 andin particular page 273 et seq., 5th Edition (1990), Verlag ChemieWeinheim). However, the tanned semifinished products described generallytend to yellow rapidly.

DE-C 38 11 267 discloses that acetalation of glutardialdehyde or otherdialdehydes which have 2 to 8 carbon atoms with short-chainalkylglycols, alkylpolyglycols, aliphatic alcohols, glycerol orsaccharides has advantageous effects. However, the vapor pressure of thedialdehydes, which are readily formed again from the veryhydrolysis-sensitive acetals, is still marked. Moreover, the performancecharacteristics of the leathers thus obtained can be further improved.

EP-A 0 066 224 discloses a process for the preparation of a precursor ofglutardialdehyde. By heating 2-alkoxy-3,4-dihydropyrans with acid andwater, a mixture of 2-hydroxy-6-alkoxytetrahydropyran,2,6-dialkoxytetrahydropyran and glutardialdehyde is obtained, the amountof undesired oligomeric and polymeric byproducts forming being onlysmall (page 2, line 33 et seq.). In the presence of water, thetetrahydropyran derivatives described liberate glutaraldehyde.

U.S. Pat. No. 2,546,018 discloses a process for the preparation ofglutaraldehyde and C-substituted glutaraldehydes which is characterizedwith hydrolysis of glutaraldehyde in an aqueous, if appropriate aqueousacidic, medium. The glutaraldehyde and C-substituted dialdehydesobtainable by the process disclosed in U.S. Pat. No. 2,546,018 arepurified by fractional distillation.

The same disadvantages with regard to tanning as those mentioned aboveare applicable to the glutaraldehyde or its derivatives obtainableaccording to EP-A 0 066 224, DE-A 44 44 709 and U.S. Pat. No. 2,546,018.

It is an object of the present invention to provide a process by meansof which versatile aqueous formulations can be provided. It is a furtherobject of the present invention to provide aqueous formulations whichare suitable as versatile reagents for the production of semifinishedproducts and of leather and which avoid the disadvantages known from theprior art. It is a further object of the present invention to provideaqueous formulations which are suitable as preservatives. Finally, it isan object of the present invention to provide uses for aqueousformulations.

We have found that these objects are achieved by the process defined atthe outset. The novel process starts from compounds of the formula I

where the variables are defined as follows.

-   X is selected from oxygen, sulfur and N—R⁶, oxygen being preferred.-   R³ and R⁶ are identical or different and are selected from-   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,    isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,    neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl,    sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl, and    n-dodecyl; preferably C₁-C₆-alkyl, such as methyl, ethyl, n-propyl,    isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,    isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl,    n-hexyl, isohexyl, sec-hexyl, particularly preferably C₁-C₄-alkyl,    such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,    sec-butyl and tert-butyl, very particularly preferably methyl;-   C₃-C₁₂-cycloalkyl, such as cyclopropyl, cyclobutyl, cyclopentyl,    cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl,    cycloundecyl and cyclododecyl; cyclopentyl, cyclohexyl and    cycloheptyl are preferred;    -   examples of substituted cycloalkyl groups are:        2-methylcyclopentyl, 3-methylcyclopentyl,        cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl        2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,        3-methylcyclohexyl, 4-methylcyclohexyl,        cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,        2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,        2-methoxycyclohexyl, 3-methoxycyclopentyl, 3-methoxycyclohexyl,        2-chlorocyclopentyl, 3-chlorocyclopentyl,        2,4-dichlorocyclopentyl, 2,2,4,4-tetrachlorocyclopentyl,        2-chlorocyclohexyl, 3-chlorocyclohexyl, 4-chlorocyclohexyl,        2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,        2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,        3-thiomethyl-cyclopentyl and 3-thiomethylcyclohexyl;-   C₇-C₁₃-aralkyl, preferably C₇- to C₁₂-phenylalkyl, such as benzyl,    1-phenethyl, 2-phenethyl, 1-phenylpropyl, 2-phenylpropyl,    3-phenylpropyl, neophyl (1-methyl-1-phenylethyl), 1-phenylbutyl,    2-phenylbutyl, 3-phenylbutyl and 4-phenylbutyl, particularly    preferably benzyl;-   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl,    2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl,    4-phenanthryl and 9-phenanthryl, preferably phenyl, 1-naphthyl and    2-naphthyl, particularly preferably unsubstituted phenyl    or substituted C₆-C₁₄-aryl, for example phenyl, 1-naphthyl,    2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl,    2-phenanthryl, 3-phenanthryl, 4-phenanthryl and 9-phenanthryl,    preferably phenyl, 1-naphthyl and 2-naphthyl, particuiarly    preferably phenyl, substituted by one or more    -   C₁-C₁₂-alkyl groups, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl and n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl and sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and        tert-butyl;    -   halogens, such as fluorine, chlorine, bromine and iodine,        chlorine and bromine being preferred;    -   C₁-C₁₂-alkoxy groups, preferably C₁-C₆-alkoxy groups, such as        methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy,        sec-butoxy, tert-butoxy, n-pentyloxy, isopentyloxy, n-hexyloxy        and isohexyloxy, particularly preferably methoxy, ethoxy,        n-propoxy and n-butoxy;        formyl,-   CO—C₁-C₁₂-alkyl, such as acetyl, propionyl, n-butyryl, isobutyryl,    sec-butyryl, tert-butyryl, n-valeroyl, isovaleroyl, sec-valeroyl,    n-capryl, n-dodecanoyl; preferably CO—C₁-C₄-alkyl, such as acetyl,    propionyl, n-butyryl, isobutyryl, sec-butyryl and tert-butyryl, very    particularly preferably acetyl;-   CO—C₃-C₁₂-cycloalkyl, such as cyclopropylcarbonyl,    cyclobutylcarbonyl, cyclopentylcarbonyl, cyclohexylcarbonyl,    cycloheptylcarbonyl, cyclooctylcarbonyl, cyclononylcarbonyl,    cyclodecylcarbonyl, cycloundecylcarbonyl and cyclododecylcarbonyl;    cyclopentylcarbonyl, cyclohexylcarbonyl and cycloheptylcarbonyl are    preferred;    -   examples of substituted cycloalkyl groups are:        2-methylcyclopentylcarbonyl, 3-methylcyclopentylcarbonyl,        2-methylcyclohexylcarbonyl, 3-methylcyclohexylcarbonyl,        4-methylcyclohexylcarbonyl, cis-2,5-dimethylcyclohexylcarbonyl,        trans-2,5-dimethylcyclohexylcarbonyl,        2-methoxycyclopentylcarbonyl, 2-methoxycyclohexylcarbonyl,        3-methoxycyclopentylcarbonyl, 3-methoxycyclohexylcarbonyl,        2-chlorocyclopentylcarbonyl, 3chlorocyclopentylcarbonyl,        2,4-dichlorocyclopentylcarbonyl, 2-chlorocyclohexylcarbonyl,        3-chlorocyclohexylcarbonyl, 4-chlorocyclohexylcarbonyl,        2,5-dichlorocyclohexylcarbonyl, 2-thiomethylcyclopentylcarbonyl,        2-thiomethylcyclohexylcarbonyl, 3-thiomethylcyclopentylcarbonyl        and 3-thiomethylcyclohexyl;-   CO—C₇-C₁₃-aralkyl, preferably CO—C₇-C₁₂-phenylalkyl, such as    phenylacetyl and ω-phenylpropionyl, particularly preferably    phenylacetyl,-   CO—C₆-C₁₄-aryl, for example benzoyl, 1-naphthoyl, 2-naphthoyl,    1-anthroyl, 2-anthroyl, 9-anthroyl, 1-phenanthroyl, 2-phenanthroyl,    3-phenanthroyl, 4-phenanthroyl and 9-phenanthroyl, preferably    benzoyl, 1-naphthoyl and 2-naphthoyl, particularly preferably    benzoyl.-   R¹, R² and R⁴ are identical or different and are selected from    hydrogen;-   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,    isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,    neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl,    sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl, and    n-dodecyl; preferably C₁-C₆-alkyl, such as methyl, ethyl, n-propyl,    isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,    isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl,    n-hexyl, isohexyl and sec-hexyl, particularly preferably    C₁-C₄-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,    isobutyl, sec-butyl and tert-butyl, very particularly preferably    methyl;-   C₃-C₁₂-cycloalkyl, substituted or unsubstituted, such as    cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,    cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl and cyclododecyl;    cyclopentyl, cyclohexyl and cycloheptyl are preferred;    -   examples of substituted cycloalkyl groups are:        2-methylcyclopentyl, 3-methylcyclopentyl,        cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl        2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,        3-methylcyclohexyl, 4-methylcyclohexyl,        cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,        2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,        2-methoxycyclohexyl, 3-methoxycyclopentyl, 3-methoxycyclohexyl,        2-chlorocyclopentyl, 3-chlorocyclopentyl,        2,4-dichlorocyclopentyl, 2,2,4,4-tetrachlorocyclopentyl,        2-chlorocyclohexyl, 3-chlorocyclohexyl, 4-chlorocyclohexyl,        2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,        2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,        3-thiomethylcyclopentyl, 3-thiomethylcyclohexyl;-   C₇-C₁₃-aralkyl, preferably C₇ to C₁₂-phenylalkyl, such as benzyl,    1-phenethyl, 2-phenethyl, 1-phenylpropyl, 2-phenylpropyl,    3-phenylpropyl, neophyl (1-methyl-1-phenylethyl), 1-phenylbutyl,    2-phenylbutyl, 3-phenylbutyl and 4-phenylbutyl, particularly    preferably benzyl;-   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl,    2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl,    4-phenanthryl and 9-phenanthryl, preferably phenyl, 1-naphthyl and    2-naphthyl, particularly preferably phenyl;    -   unsubstituted or substituted-   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl,    2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl,    4-phenanthryl and 9-phenanthryl, preferably phenyl, 1-naphthyl and    2-Naphthyl, particularly preferably phenyl, unsubstituted or    substituted by one or more    -   C₁-C₁₂-alkyl groups, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl and n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl and sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and        tert-butyl;    -   halogens, such as fluorine, chlorine, bromine and iodine,        chlorine and bromine being preferred;    -   C₁-C₁₂-alkoxy groups. preferably C₁-C₆-alkoxy groups, such as        methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy,        sec-butoxy, tert-butoxy, n-pentyloxy, isopentyloxy, n-hexyloxy        and isohexyloxy, particularly preferably methoxy, ethoxy,        n-propoxy and n-butoxy;-    it being possible in each case for two neighboring radicals to be    linked to one another with formation of a ring. Thus, R¹ and R²    together may be, for example, C₁-C₈-alkylene, unsubstituted or    substituted by, for example, C₁-C₁₂-alkyl or C₆-C₁₄-aryl. Examples    are: —CH₂—, —CH(CH₃)—, —(CH₂)₂—, —CH₂—CH(CH₃)—, —CH₂—CH(C₂H₅)—,    —(CH₂)₃—, —(CH₂)₂—CH(CH₃)—, —(CH₂)₂—CH(C₂H₅)—, —(CH₂)₂—CH(C₆H₅)—,    —(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆—, —(CH₂)₇—, —CH(CH₃)—CH₂—CH₂—CH(CH₃)—,    —CH(CH₃)—CH₂—CH₂—CH₂—CH(CH₃)—, preferably C₃-C₅-alkylene, such as    —(CH₂)₃—, —(CH₂)₄— and —(CH₂)₅—.-   n is an integer from 1 to 4, in particular 2 or 3;-   R⁵ are identical or different and are selected from hydrogen;-   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,    isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,    neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl,    sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl, and    n-dodecyl; preferably C₁-C₆-alkyl, such as methyl, ethyl, n-propyl,    isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,    isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl,    n-hexyl, isohexyl and sec-hexyl, particularly preferably    C₁-C₄-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,    isobutyl, sec-butyl and tert-butyl, very particularly preferably    methyl;-   C₃-C₁₂-cycloalkyl, substituted or unsubstituted, such as    cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,    cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl and cyclododecyl;    cyclopentyl, cyclohexyl and cycloheptyl are preferred;    -   examples of substituted cycloalkyl groups are:        2-methylcyclopentyl, 3-methylcyclopentyl,        cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl        2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,        3-methylcyclohexyl, 4-methylcyclohexyl,        cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,        2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,        2-methoxycyclohexyl, 3-methoxycyclopentyl, 3-methoxycyclohexyl,        2-chlorocyclopentyl, 3-chlorocyclopentyl,        2,4-dichlorocyclopentyl, 2,2,4,4-tetrachlorocyclopentyl,        2-chlorocyclohexyl, 3-chlorocyclohexyl, 4-chlorocyclohexyl,        2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,        2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,        3-thiomethyl-cyclopentyl and 3-thiomethylcyclohexyl;-   C₇-C₁₃-aralkyl, preferably C₇- to C₁₂-phenylalkyl, such as benzyl,    1-phenethyl, 2-phenethyl, 1-phenylpropyl, 2-phenylpropyl,    3-phenylpropyl, neophyl (1-methyl-1-phenylethyl), 1-phenylbutyl,    2-phenylbutyl, 3-phenylbutyl and 4-phenylbutyl, particularly    preferably benzyl;-   C₆-C₁₄-aryl, substituted or unsubstituted, substituted and    unsubstituted C₆-C₁₄-aryl radicals being defined as above.

In an embodiment of the present invention, R⁵ may be linked to R² or R⁵to R⁴ or R⁵ to R³ or, where n is greater than 1, in each case twoneighboring radicals R⁵ may be linked to one another with formation of aring. Thus, R⁵ and R² together may be, for example, C₁-C₈-alkylene,unsubstituted or substituted by C₁-C₁₂-alkyl or C₆-C₁₄-aryl. Examplesare: —CH₂—, —CH(CH₃)—, —(CH₂)₂—, —CH₂—CH(CH₃)—, —CH₂—CH(C₂H₅)—,—(CH₂)₃—, —(CH₂)₂—CH(CH₃)—, —(CH₂)₂—CH(C₂H₅)—, —(CH₂)₂—CH(C₆H₅)—,—(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆, —(CH₂)₇—, —CH(CH₃)—CH₂—CH₂—CH(CH₃)—,—CH(CH₃)—CH₂—CH₂—CH₂—CH(CH₃)—, preferably. C₃-C₅-alkylene, such as—(CH₂)₃—, —(CH₂)₄—, —(CH₂)₅—.

R² to R⁵ are very particularly preferably each hydrogen.2-Methoxy-2,3-dihydro-4H-pyran (formula I.1) is very particularlypreferably selected as a compound of the formula I.

According to the invention, a cyclic compound of the formula I is heatedin the presence of water. The amount of water may be chosen within wideranges, and is preferably from 20 to 1 000, particularly preferably from50 to 500, very particularly preferably from 60 to 200, % by volume,based on the cyclic compound of the formula I.

The novel process is carried out in the presence of an acidic catalystwhich may consist of one or more acidic compounds.

Suitable acidic catalysts are, for example, phosphoric acid, inparticular ortho-phosphoric acid, formic acid, acetic acid, acidicsilica gels, acidic alumina, sulfuric acid, sulfonic acids, such asmethanesulfonic acid or para-toluenesulfonic acid. Mixtures of, forexample, sulfuric acid and phosphoric acid are also suitable. Ifnonaqueous solvents are employed, the use of P₂O₅ or a molecular sieveis conceivable. From 0.1 to 20% by weight, based on the cyclic compoundof the formula I, of catalyst can be used. Of course, the catalyst orthe catalysts can also be diluted, for example with water, before beingused in the novel process.

In an embodiment of the present invention, the novel process is carriedout at acidic pH, i.e. for example at a pH which is from 0 to 6.8,preferably from 0.1 to 4, particularly preferably from 0.5 to 4.

In an embodiment of the present invention, the novel process is carriedout at from 40 to 120° C., in particular from 50 to 85° C.

The novel process can be carried out at any desired pressures from 0.1to 100 bar, atmospheric pressure being preferred.

From 10 minutes to 24 hours, preferably from one to three hours areexpedient as a time for the heating.

According to the invention, heating can be effected in the presence ofan organic solvent or of a mixture of organic solvents, for exampletoluene, petroleum ether or n-heptane, but the addition of solvent isnot necessary. If it is desired to use a solvent, an amount of from 10to 100% by volume, based on the cyclic compound of the formula I, issuitable.

In a preferred embodiment of the present invention, the novel process iscarried out without addition of ketone or monoaldehydes, examples ofketones are acetone, methyl ethyl ketone and methyl isobutyl ketone.Examples of monoaldehydes are acetaldehyde, benzaldehyde, crotonaldehydeand propionaldehyde.

During or after the heating, H—X—R³ formed during the heating isseparated off at least partially.

While the novel process is being carried out, H—X—R³ is formed, inparticular in an amount of up to one equivalent per cyclic compound ofthe formula I which is used.

In an embodiment of the present invention, H—X—R³ is separated offduring the heating, i.e. during the reaction, for example bydistillation, the material stream separated off, which contains H—X—R³and may furthermore contain solvent, being admixed again only partiallyor not at all with the reaction mixture.

In another embodiment of the present invention, heating is firsteffected without separating off H—X—R³, for example to reflux or tosomewhat lower temperature than reflux, and separating off H—X—R³ isbegun after some time.

If H—X—R³ is obtained in crystalline form, it can be separated off byfiltration, preferably after the end of the reaction and cooling of thereaction mixture to, for example, room temperature.

In the context of the present invention, it is also possible first toeffect heating without separating off H—X—R³ and then to separate offH—X—R³ at least partially by applying reduced pressure.

In the context of the present invention, separating off H—X—R³ at leastpartially is to be understood as meaning that at least 30, preferably atleast 85, particularly preferably at least 95, mol % of the H—X—R³formed during the novel process is separated off. H—X—R³ can beseparated off quantitatively, which is preferred particularly whenH—X—R³ has toxicologically unacceptable properties.

In a variant of the novel process, up to 99.5 mol % of the H—X—R³ formedduring the heating is separated off, and in a further variant up to 99.8mol %.

On separating off H—X—R³, water may also be partially separated off. Inthe present invention, however, quantitative separation of water isavoided.

The novel process gives aqueous formulations which are likewise asubject of the present invention and are also referred to below as novelaqueous formulations.

Before, during or after the novel, at least partial separation ofH—X—R³, the usually acidic novel aqueous formulations can be completelyor partly neutralized. For example, basic alkali metal salts, such asalkali metal hydroxides, alkali metal carbonates and alkali metalbicarbonates, are suitable for the neutralization. Basic salts of sodiumand potassium are particularly suitable. Basic salts of magnesium, forexample magnesium oxide, are also suitable.

In some cases, the formation of a multiphase mixture is observed whilecarrying out the novel process. In said cases, it is possible to removethe respective aqueous phase by, for example, decanting or other methodsknown per se.

In a preferred embodiment of the present invention, a cyclic compound ofthe formula I is heated in the presence of at least one compound of theformula II

where, in formula II,

-   R⁷ are different or preferably identical and are selected from-   C₁-C₄-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,    isobutyl, sec-butyl and tert-butyl, very particularly preferably    methyl, and in particular hydrogen.-   x is an integer from 1 to 250, preferably from 3 to 50, particularly    preferably from 5 to 20.-   y is selected from zero and 1.

Examples of compounds of the formula II are ethylene glycol, propyleneglycol, glycerol, diethylene glycol, dipropylene glycol, diglycerol(R⁷=hydrogen, x=2, y=1), triethylene glycol, tetraethylene glycol andpolyethylene glycols, for example polyethylene glycols having on averagefrom 8 to 25 ethylene oxide units (number average), and furthermoremixed polyalkylene oxides which are obtainable, for example, by reactingmixtures of ethylene oxide and propylene oxide and, if appropriate,butylene oxide. Polyethylene glycol having on average from 7 to 12ethylene oxide units (number average) and glycerol are particularlypreferred.

If it is desired, according to the invention, to effect heating in thepresence of at least one compound of the formula II, it is possible tochoose from 3 to 300, preferably from 5 to 200, particularly preferablyfrom 10 to 50%, by weight, based on the cyclic compound of the formulaI, of a compound of the formula II.

The present invention furthermore relates to aqueous formulationsobtainable by the novel process.

Novel aqueous formulations may have a water content of from 5 to 80,preferably from 20 to 50, % by weight. In the context of the presentinvention, the remainder of the novel formulations to 100% by weight isalso referred to as active substance content of the novel formulations,and the reaction products resulting from the novel reaction describedabove, if appropriate as a mixture with unconverted cyclic compound ofthe formula I and, if appropriate, as a mixture with the compound of theformula II, are referred to as active substances.

Novel aqueous formulations may have a pH of from 2 to 9, preferably from3 to 7, particularly preferably from 4 to 6.

For example, by means of mass spectrometry, it is possible to show thatnovel aqueous formulations contain only small amounts of dicarbonylcompound of the formula III

for example up to 10% by weight, and substantially, for example, dimers,oligomers and polymers of dicarbonyl compound of the formula III whichare formed by aldol condensation. The variables are as defined above.

The present invention furthermore relates to mixtures of dimers,oligomers and polymers of compound of the formula II, which may becontaminated by small amounts, for example up to 10% by weight, ofcompound of the formula III. Novel mixtures of dimers, oligomers andpolymers can be obtained by the novel preparation process and subsequentisolation by methods known per se, for example removal, in particularevaporation, of water. Novel mixtures of dimers, oligomers and polymersof compound III may have a broad molecular weight distribution; thus,the average molecular weight M_(n) may be from 100 to 100 000,preferably from 200 to 10 000, g/mol and the quotient M_(w)/M_(n) may befrom 2 to 20, preferably from 2.1 to 10.

Novel mixtures of dimers, oligomers and polymers of the compound of theformula III can be used without further processing or as an aqueousformulation for the production of semifinished products and of leatherand as a preservative, in particular directly or as a pulverulentformulation.

The present invention furthermore relates to the use of the novelaqueous formulations for the production of semifinished products and ofleather. The present invention furthermore relates to a process for theproduction of semifinished products or leather using at least one novelaqueous formulation.

In an embodiment of the present invention, novel aqueous formulationsare used for the pretanning, tanning or retanning of animal hides.

The present invention furthermore relates to the use of novel aqueousformulations for the pretanning, tanning or retanning of animal hidesand a process for the pretanning, tanning or retanning of animal hidesusing novel aqueous formulations.

The novel process for the pretanning, tanning or retanning of animalhides, (also referred to below as novel tanning process) starts fromhides of animals, such as cattle, pigs, goats or deer, which have beenpretreated by conventional methods. It is not important for the noveltanning process whether the animals were killed by slaughtering or diedof natural causes. The conventional methods of pretreatment include, forexample, liming, deliming, bating and pickling, and mechanicaloperations, for example for fleshing the hides.

The novel tanning process is usually carried out in the presence ofwater.

The novel tanning process is carried out, for example, by a procedure inwhich one or more novel aqueous formulations are added in one portion orin a plurality of portions immediately before or during the tanningstep.

The novel tanning process is preferably carried out at a pH of from 2.5to 4, it frequently being observed that the pH increases by about 0.3 tothree units while the novel tanning process is being carried out. The pHcan be increased by about 0.3 to three units by adding basifying agents.

The novel tanning process is carried out in general at from 10 to 45°C., preferably from 20 to 30° C. A duration of from 10 minutes to 12hours, preferably from one to 3 hours, has proven useful. The noveltanning process can be carried out in any desired vessels customary inthe tannery, for example by drumming in barrels or in rotatable drumshaving internals.

In a variant of the novel tanning process, one or more novel aqueousformulations are used together with one or more conventional tanningagents, for example with chrome tanning agents, mineral tanning agents,syntans, polymer tanning agents or vegetable tanning agents, asdescribed, for example, in Ullmann's Encyclopedia of IndustrialChemistry, Volume A15, pages 259 to 282 and in particular page 268 etseq., 5th Edition (1990), Verlag Chemie Weinheim. The weight ratio ofnovel formulation to conventional tanning agents or the sum ofconventional tanning agents is expediently from 0.01:1 to 100:1. In anadvantageous variant of the novel process, only a few ppm of theconventional tanning agents are added to the novel formulations.However, it is particularly advantageous completely to dispense with themixing of conventional tanning agents with novel formulations.

In a variant of the novel tanning process, one or more novel aqueousformulations are added in one portion or in a plurality of portionsbefore or during the pretanning, in a particular variant as early asduring pickling.

In a further variant of the novel tanning process, one or more novelaqueous formulations are added in one portion or in a plurality ofportions before or during a retanning step. This variant is alsoreferred to below as novel retanning process. The novel retanningprocess starts from pretanned hides, which are also referred to assemifinished products. These are treated with the novel aqueousformulations.

The novel retanning process can be carried out under otherwiseconventional conditions. One or more, for example from 2 to 6, soakingsteps are expediently chosen and washing with water can be effectedbetween the soaking steps. The temperature during the individual soakingstep is in each case from 5 to 60° C., preferably from 20 to 45° C.Further compositions usually used during the retanning, for examplefatliquoring agents, leather dyes or emulsifiers, are expedientlyemployed.

A further aspect of the present invention relates to semifinishedproducts and leather produced by the novel tanning process. Novelleathers and novel semifinished products are produced using at least onenovel aqueous formulation. Novel leathers and semifinished products havean overall advantageous quality, for example smooth grain, relativelyhomogeneous tanning over the cross section, improved tensile strengthand body and less tendency to discoloration, in particular to yellowing.

In a special embodiment of the novel tanning process, novel formulationsare used in the form of pulverulent formulations. The present inventiontherefore furthermore relates to the use of novel aqueous formulationsfor the preparation of pulverulent formulations and a process for thepreparation of pulverulent formulations using novel aqueousformulations.

For the preparation of novel pulverulent formulations, for example, aprocedure is adopted in which at least one novel aqueous formulation isdried, for example by evaporating the water and particularly preferablyby spray-drying.

In a particular embodiment of the present invention, at least one novelaqueous formulation is mixed with one or more additives and then dried,for example by evaporating the water and in particular by spray-drying.

Suitable additives are as a rule solid particulate substances. They arepreferably selected from starch, silica, for example in the form ofsilica gel, in particular in the form of spheroidal silica gels, sheetsilicates, alumina and mixed oxides of silicon and aluminum.

In a special embodiment of the present invention, the followingprocedure is adopted: it has proven useful first to concentrate novelaqueous formulations to a residual water content of 50% by weight orless. Furthermore, if desired, one or more additives are added. Theremaining volatile components are then removed. The resulting liquid,solid or oily concentrated formulations are preferably atomized in aspray dryer, preferably in a spray tower. Spray dryers are known to aperson skilled in the art and are described, for example, inVauck/Müller, Grundoperationen chemischer Verfahrenstechnik, VCHWeinheim, 1988, 7th Edition, pages 638-740 and pages 765-766, and in theliterature cited therein.

The present invention furthermore relates to pulverulent formulationscomprising

from 10 to 100, preferably from 40 to 90, % by weight of activesubstance and from 0 to 90, preferably from 10 to 60, % by weight of oneor more additives.

The novel pulverulent formulations may consist of fine particles havinga mean particle diameter of from 100 nm to 0.1 mm. The particlediameters have a particle diameter distribution which may be narrow orbroad. Bimodal particle size distributions are also conceivable. Theparticles themselves may have an irregular or spherical shape, sphericalparticle shapes being preferred. The novel pulverulent formulations canbe metered under particularly hygienic conditions in the novel tanningprocess and are used instead of novel aqueous formulations.

It has furthermore been found that novel aqueous formulations and novelpulverulent formulations have a biocidal action.

A further aspect of the present invention relates to the use of thenovel aqueous formulations and of the novel pulverulent formulations forpreservation, and preservatives comprising novel pulverulent or aqueousformulations. The novel preservatives are suitable for the preservationof products, for example cosmetic products, and of surfaces.

The examples which follow illustrate the invention.

1. Preparation of the Novel Aqueous Formulations 1.1 to 1.3

The molecular weight determinations were carried out by gel permeationchromatography.

Stationary phase: Poly-(2-hydroxyethyl methacrylate) gel crosslinkedwith ethylene glycol dimethacrylate, commercially available as HEMA BIOfrom PSS, Mainz, Germany.

-   Mobile phase: Mixture of 30% by weight of tetrahydrofuran (THF), 10%    by weight of acetonitrile, 60% by weight of 0.1 molar aqueous NaNO₃    solution-   Internal standard: 0.001% by weight of benzophenone-   Flow rate: 1.5 ml/min-   Concentration: 1% by weight in the mobile phase with internal    standard-   Detection: UV/VIS at 254 nm    Calibration with polystyrene sulfonate calibration unit from PPS.    1.1. Preparation of Aqueous Formulation 1.1

In a 2 liter three-necked flask having a condenser, stirrer andthermometer, 200 g of 2-methoxy-2,3-dihydro-4H-pyran (formula I.1; 2mol), 30 g of polyethylene glycol having an average molecular weightM_(n) of 400 g/mol, 200 ml of water and 6.5 g of a 50% by weight aqueoussulfuric acid were mixed and were heated to 77° C. for 3 hours. The pHwas 1.

Thereafter, cooling to 35° C. was effected and the pH was then broughtto 5 with 25% by weight of aqueous sodium hydroxide solution.Thereafter, heating to 56° C. was effected, stirring was carried out at150 mbar for 3 hours and aqueous methanol was separated off.

400 g of novel aqueous formulation 1.1.

-   M_(n): 580 g/mol, M_(w): 1363 g/mol, M_(w)/M_(n): 2.58    1.2. Preparation of Aqueous Formulation 1.2

In a 1 liter three-necked flask having a condenser, stirrer andthermometer, 300 g of 2-methoxy-2,3-dihydro-4H-pyran (formula I.1; 2.9mol), 200 ml of water and 4.2 g of 50% by weight sulfuric acid weremixed and were heated to 80° C. for 1 hour. The pH was 1.

Thereafter, cooling to 35° C. was effected and the pH was then broughtto 6 with 18 g of 10% by weight of aqueous sodium hydroxide solution.Thereafter, stirring was carried out at from 35 to 45° C. and from 80 to100 mbar for 3 hours and aqueous methanol was separated off.

370 g of novel aqueous formulation 1.2 were obtained.

-   M_(n): 326 g/mol, M_(w): 660 g/mol, M_(w)/M_(n): 2.02    1.3. Preparation of Aqueous Formulation 1.3

In a 1 liter three-necked flask having a condenser, stirrer andthermometer, 300 g of 2-methoxy-2,3-dihydro-4H-pyran (formula I.1; 2.9mol), 200 ml of water and 6.7 g of 50% by weight sulfuric acid weremixed and were heated to 80° C. for 1 hour. The pH was kept at 0.5during the reaction by adding further sulfuric acid. Thereafter, coolingto 30° C. was effected and the pH was brought to 6 with 33 g of 10% byweight of aqueous sodium hydroxide solution. Thereafter, stirring wascarried out at 30° C. and from 60 to 70 mbar for 3 hours and aqueousmethanol was separated off.

300 g of novel aqueous formulation 1.3 were obtained.

-   

M_(n): 400 g/mol, M_(w): 455 g/mol, M_(w)/M_(n): 2.39

2. Novel Tanning Experiments 2.1 to 2.3 and Comparative Experiment

Data in % by weight are based on the pickled weight, unless statedotherwise.

750 ml of water and 3% by weight, based on the pickled pelt, of a novelaqueous formulation according to examples 1.1. to 1.3. were added tostrips, each weighing 2500 g, of a pickled cattle pelt having a splitthickness of 2.5 mm, at a pH of 3.0-3.2 and 25° C., in a 10 I drum.After a drumming time of 60 minutes, 2% by weight of the sulfone tanningagent from EP-B 0 459 168, example K1, were added and drumming waseffected for a further 2 hours. The pH was then brought to 4.9-5.1 with0.5% by weight of magnesium oxide in the course of 6 hours. The liquorwas discharged and the hide was washed with 300 ml of water. Aftersamming, the hides were shaved to 1.6-1.8 mm. The novel semifinishedproducts 2.1 to 2.3 were obtained.

The shaveability was determined by experiments on a shaving machine. Theshaving machine operated with rotating blades. In the case of poorshaveability, the knives slid over the surface and the temperature onthe surface of the leathers increased so that melting of a hornysubstance irreversibly damaged the hide. The rating was based on arating system from 1 (very good) to 5 (poor).

Comparative experiment C 2.4 was carried out analogously, except thatthe novel adduct was replaced by 3% by weight of glutaraldehyde (50% byweight aqueous solution).

The shrinkage temperatures were determined by the method from DIN 53 336(year 1977), the method having been modified as follows:

-   Point 4.1: The sample pieces had the dimensions 3 cm·1 cm; the    thickness was not determined.-   Point 4.2: Only one specimen instead of 2 specimens was tested per    leather sample.-   Point 6: Omitted-   Point 7: The drying in a desiccator under reduced pressure was    omitted.-   Point 8: The shrinkage temperature was measured when the pointer    moved back.

The rating of the shaveability and of the yellowing were effectedaccording to the following rating system: 1 very good, 2 good, 3satisfactory, 4 adequate. TABLE 1 Result of tanning and analyticalevaluation of the novel semifinished products Shrinkage Semifinishedtemperature Number product Shaveability [° C.] Yellowing 2.1 2.1 3 761.5 2.2 2.2 2 77.5 2.5 2.3 2.3 2 79 2 C 2.4 Glutaraldehyde 4 77 43. Production of Novel Leathers and Comparative Experiment

Data in % by weight are based on the shaved weight, unless statedotherwise.

3.1. Production of the Leather 3.1 from Semifinished Product 2.1

1800 g of semifinished product 2.1 were drummed together with thefollowing agents for 20 minutes:

-   120% by weight of water, 5% by weight of the sulfone tanning agent    from EP-B 0 459 168, example K1, and-   4% by weight of a 30% by weight aqueous, partly NaOH-neutralized    solution of a methacrylic acid homopolymer having the following    analytical data: M_(n) about 10 000; Fikentscher K value: 12    (determined as a 1% by weight aqueous solution), viscosity of the    30% by weight solution: 65 mPa·s (DIN EN ISO 3219, 23° C.), pH 5.1.-   6% by weight of the vegetable tanning agent Tara® (BASF    Aktiengesellschaft) and 2% by weight of the resin tanning agent    Relugan® S (BASF Aktiengesellschaft) and 2% by weight of an aqueous    solution of dyes whose solids had the following composition:-   70 parts by weight of dye from EP-B 0 970 148, example 2.18,-   30 parts by weight of Acid Brown 75 (iron complex), Colour Index    1.7.16.    were then metered and the mixture was drummed. After two hours, the    pH was brought to 3.6 with formic acid. 6% by weight of a    fatliquoring agent (cf. 4.) and 1% by weight of Lipamin OK® (BASF    Aktiengesellschaft) were added as a fatliquoring component. After a    drumming time of a further 60 minutes, the pH was brought to 3.2    with formic acid. Before the liquor was discharged, a sample of the    liquor was taken. The liquor was discharged.

The leather thus obtained was washed twice with 100% by weight of watereach time, stored moist overnight, sammed and then dried on a toggleframe at 50° C. Leather 3.1 was obtained. After staking, leather 3.1 wasassessed as below.

The evaluation was carried out according to a rating system from 1 (verygood) to 5 (poor). The evaluation of the liquor exhaustion was effectedvisually according to the criteria of residual dye (extinction) andturbidity (fatliquoring agent), from which the mean value wascalculated.

EXAMPLES 3.2 TO 3.3, COMPARATIVE EXAMPLE C 3.4

The above example was repeated, but in each case with the novelsemifinished products 2.2 to 2.3. For comparative example C3.4, thesemifinished product from example C2.4 was further processed. Theevaluation of the performance characteristics is shown in table 2. TABLE2 Grain Tensile Stitch tear Liquor tight- Soft- strength resistanceLevel- Leather exhaustion Body ness ness [N] [N] ness 3.1 2 2.5 3 2.5268 186 2.5 3.2 2.5 2.5 2 1.5 264 190 2 3.3 2 1.5 1.5 2 280 194 1.5 C3.4 3 3.5 3.5 3 247 191 3

The tensile strength was determined according to DIN 53328.

The stitch tear resistance was determined according to DIN 53331.

4. Preparation of the Fatliquoring Agent for Examples 2.1 to 2.3 andC2.4

The following were mixed in a 2 l kettle:

-   230 g of a polyisobutene having M_(n)=1000 g/mol and M_(w)=2000    g/mol-   30 g of n-C₁₈H₃₇O—(CH₂CH₂O)₂₅—OH-   5 g of n-C₁₈H₃₇O—(CH₂CH₂O)₈₀—OH-   40 g of oleic acid-   230 g of sulfited oxidized triolein

The mixture was heated to 60° C. with stirring, and 470 g of water and10 g of n-C₁₆H₃₃O—(CH₂CH₂O)₇—OH were added. The resulting emulsion wasthen passed through a gap homogenizer. A finely divided, stable emulsionwas obtained.

1. A process for the preparation of aqueous formulations, wherein atleast one cyclic compound of the formula I

is heated in the presence of water and of an acidic catalyst and, duringor after the heating, H—X—R³ is separated off at least partially, where,in formula I, X is selected from oxygen, sulfur and N—R⁶, R³ and R⁶ areidentical or different and are selected from C₁-C₁₂-alkyl,C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃-aralkyl,C₆-C₁₄-aryl, substituted or unsubstituted, formyl, CO—C₁-C₁₂-alkyl,CO—C₃-C₁₂-cycloalkyl, substituted or unsubstituted, CO—C₇-C₁₃-aralkyl,CO—C₆-C₁₄-aryl, where, if X is N—R⁶, R³ and R⁶ may be linked to oneanother with formation of a ring; R¹, R² and R⁴ are identical ordifferent and are selected from hydrogen, C₁-C₁₂-alkyl,C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃-aralkyl,C₆-C₁₄-aryl, substituted or unsubstituted, it being possible in eachcase for two neighboring radicals to be linked to one another withformation of a ring; n is an integer from 1 to 4; R⁵ are identical ordifferent and are selected from hydrogen, C₁-C₁₂-alkyl,C₃-C₁₂-cycloalkyl, substituted or unsubstituted, c₇-C₁₃-aralkyl,c₆-C₁₄-aryl, substituted or unsubstituted, it being possible for R⁵ tobe linked to R⁴ or in each case two neighboring radicals R⁵ to be linkedto one another with formation of a ring.
 2. A process according to claim1, wherein it is carried out without addition of ketone or monoaldehyde.3. A process according to claim 1 or 2, wherein X is oxygen.
 4. Aprocess according to any of claims 1 to 3, wherein R¹, R², R⁴ and R⁵ areeach hydrogen.
 5. A process according to any of claims 1 to 4, wherein nis chosen to be
 2. 6. A process according to any of claims 1 to 5,wherein the heating is carried out in the presence of at least onecompound of the formula II

where, in formula II, R⁷ are identical or different and are selectedfrom hydrogen and C₁-C₄-alkyl, x is an integer from 1 to 250 and y isselected from zero and
 1. 7. An aqueous formulation obtainable by aprocess according to any of claims 1 to
 6. 8. A mixture of dimers,oligomers and polymers of at least one dicarbonyl compound of theformula III

where R¹, R² and R⁴ are identical or different and are selected fromhydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted,C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or unsubstituted, it beingpossible in each case for two neighboring radicals to be linked to oneanother with formation of a ring; n is an integer from 1 to 4; R⁵ areidentical or different and are selected from hydrogen, C₁-C₁₂-alkyl,C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃-aralkyl,C₆-C₁₄-aryl, substituted or unsubstituted, it being possible for R⁵ tobe linked to R⁴ or in each case two neighboring radicals R⁵ to be linkedto one another with formation of a ring.
 9. A mixture according to claim8, obtainable by a process according to any of claims 1 to 6 andsubsequent removal of water.
 10. The use of an aqueous formulationaccording to claim 7 or a mixture according to claim 8 or 9 for theproduction of semifinished products and of leather.
 11. A process forthe production of semifinished products or leather using an aqueousformulation according to claim 7 or a mixture according to claim 8 or 9.12. The use of the aqueous formulation according to claim 7 for thepreparation of pulverulent formulations.
 13. A process for thepreparation of pulverulent formulations using an aqueous formulationaccording to claim
 7. 14. A process according to claim 13, wherein atleast one aqueous formulation according to claim 7 and, if appropriate,one or more additives are mixed with one another and then dried.
 15. Aprocess according to claim 14, in which the additive or additives areselected from starch, silica, sheet silicates, alumina and mixed oxidesof silicon and aluminum.
 16. A process for the preparation of apulverulent formulation according to claim 14 or 15, which is obtainedby spray-drying.
 17. A pulverulent formulation obtainable according toany of claims 13 to
 16. 18. A semifinished product or leather producedusing at least one aqueous formulation according to claim 7 or at leastone pulverulent formulation according to claim
 17. 19. The use of apulveruleni formulation according to claim 17 or of an aqueousformulation according to claim 7 or a mixture according to claim 8 or 9as a preservative.